AC not working, Heating does

Ok, my central air doesn't work, my central heat does. Took the panel off the unit and found out:
Blue (Rc) - Yellow = 0 volts Red (Rh) - White = 24 volts AC
The furnace is new, put in last year by a professional installer. The AC is old, and may or may not have problems of its own (I've not had the house long enough to need it)
My pal Google tells me there may be a fuse on the board, which I will check tomorrow. But wouldn't a blown fuse keep anything from working? If the fuse is good, I'm guessing the board is bad, but with it being new that seems unlikely. Anything else I should check?
Thanks.
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On Sun, 03 Jun 2007 20:27:41 -0400, Kitep wrote:

Check for 24 volts going out to the outside unit's contactor when cooling is call for by the thermostat.
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The outside unit is wired to the same screws the blue (Rc) and yellow thermostat wires go to on the main unit. If I'm getting 0 volts there, I'm pretty sure I'm getting 0 volts outside. Thanks for the suggestion though.
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You will get zero volts a the thermostat , this is normal because the common side of the control transformer dose not go to the thermostat and to get a voltage reading you would need to check from common to red RH (or blue RC), (transformer power), common to yellow (for cooling) common to white (for heating) common to green (for fan relay) Checking the two thermostat wires AT the outside unit should show a 24 volt reading IF the thermostat is calling for cooling..
As a test for cooling, you can bypass the thermostat by jumpering RC to Yellow which will bring on the outside unit and the indoor fan if set on auto (Naturally, if set on "on" the indoor fan willl already be running) Same for a thermostat bypass test for heating only jumpering from RH to white will bring on the heat (but not the fan right away).
Most thermostats have a jumper wire from RH (red-heat) to RC (red cool) and the jumper is to be removed IF there is a second transformer in the outdoor unit. IF you are getting 24 volts at the thermostat it's because you are checking across an open set of contacts and picking up the common side of the transformer from the contactor (in series). Also if you are getting 24 volts, the fuse is not blown.
Kitep wrote:

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Thanks, that's pretty much what the guy who came out to check it said. The Rh & Rc should have been jumpered together at the thermostat with the blue wire not hooked to anything. People say money can't buy happiness, but it did for me :)

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Sure sounds like your installer didn't wire it correctly. Call him (her) back. Let us know how things go.
Or call another company and ask for a service tech.
--

Christopher A. Young
You can\'t shout down a troll.
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